Polyphenylene ether resin concentrates containing organic phosphates

ABSTRACT

The invention relates to a process for the manufacture of a thermoplastic composition comprising a polyphenylene ether resin and a styrenic resin wherein the processes comprises a concentrate of polyphenylene ether resin with an organic phosphate compound. The concentrate allows for ease of handling of polyphenylene ether resin without the risk of dust ignition while obtaining substantially the same physical properties as obtained with polyphenylene ether resin powder. The invention also relates to articles formed out of the compositions made by the process of the invention.

This is a divisional of co-pending pending prior application Ser. No.09/285,574 filed on Apr. 2, 1999, now U.S. Pat. No. 6,258,879, which isincorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process for the manufacture of thermoplasticcomposition. In particular, the invention relates to a process for themanufacture of a thermoplastic composition comprising polyphenyleneether resin.

The invention also relates to articles formed out of the compositionsmade by the process of the invention.

2. Brief Description of the Related Art

Poly(phenylene ether) resins (referred to hereafter as “PPE”) arecommercially attractive materials because of their unique combination ofphysical, chemical, and electrical properties. Commercially, most PPEare sold as blends with predominantly high impact polystyrene resins.PPE are miscible with polystyrene resins in all proportions and becauseof the very high glass transition temperatures of PPE, the blends of PPEwith polystyrene resins possess higher heat resistance than that of thepolystyrene resins alone. Moreover, the combination of PPE with highimpact polystyrene resins results in additional overall properties suchas high flow and ductility. Examples of such blends can be found in U.S.Pat. Nos. 3,383,435; 4,097,550; 4,113,800; 4,101,503; 4,101,504;4,101,505; 4,128,602; 4,139,574; and 4,154,712 among others. Theproperties of these blends can be further enhanced by the addition ofvarious additives such as impact modifiers, flame retardants, lightstabilizers, processing stabilizers, heat stabilizers, antioxidants andfillers.

Commercial PPE are produced as a relatively fine powder form typicallyhaving at least 10% by weight, often at least 20% by weight fineparticles of less than about 75 microns in size. Particles less thanabout 75 microns in size are believed to lead to dust explosion hazards.Consequently these powders require special handling procedures tocontrol dust and potential spark ignition hazards associated with suchpowders. Such handling procedures include grounding of equipment and useof inert gas blankets to exclude oxygen. It would be commerciallyadvantageous to be able to ship PPE to various locations around theworld for compounding into resin compositions to serve local marketneeds. However, the handling procedures as described above requiresignificant investment for equipment modifications and consequentlylimit the commercial feasibility for such compounding flexibility.Conversion of PPE powder using standard compounding extruders followedby pelletization of the extrudate to obtain pellets having dimensions ofabout 3 mm by 3 mm has been attempted as a solution to the problemsassociated by PPE powder. Unfortunately, the physical properties of manyresin compositions made using the pellets are inferior as compared tocontrol compositions made with PPE powder and the pellets must be groundto a smaller size in order to obtain physical properties that closelyapproximate those of control compositions. Consequently, the utility ofthe PPE pellet approach has been limited.

It is therefore apparent there continues to be a need for improvedprocesses to manufacture resin compositions containing PPE.

SUMMARY OF THE INVENTION

The needs discussed above have been generally satisfied by the discoveryof a process for the manufacture of a thermoplastic compositioncontaining:

a) at least one polyphenylene ether resin, and

b) optionally, at least one polystyrene resin;

wherein the process comprises preparing a concentrate of polyphenyleneether resin with an organic phosphate compound. The composition mayfurther comprise at least one of the following optional components:thermoplastic resins such as, for example, polyolefins, polyetherimides,polyethersulfones, polysulfones, polyamides, polyesters, and polyarylenesulfides, compatibilizers, impact modifiers, anti-oxidants, flameretardants, drip suppressers, crystallization nucleators, dyes,pigments, colorants, reinforcing agents, fillers, stabilizers, andantistatic agents.

The description which follows provides further details regarding thisinvention.

DESCRIPTION OF THE DRAWINGS.

Not applicable.

DETAILED DESCRIPTION OF THE INVENTION

A process for the manufacture of a thermoplastic composition comprisespreparing a solid concentrate comprising a polyphenylene ether resin andan organic phosphate compound, wherein said solid concentrate has lessthan 5% by weight, and preferably less than 1% by weight, of particlesless than about 75 micrometers. The concentrate allows for ease ofhandling of polyphenylene ether resin while obtaining substantially thesame physical properties as obtained with polyphenylene ether resinpowder.

The invention also relates to articles formed out of the compositionsmade by the process of the invention.

Polyphenylene ether resin, hereinafter “PPE”, per se, are known polymerscomprising a plurality of structural units of the formula (I):

wherein for each structural unit, each Q¹ is independently halogen,primary or secondary lower alkyl (e.g., alkyl containing up to 7 carbonatoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; and each Q² is independently hydrogen,halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹. Preferably, eachQ¹ is alkyl or phenyl, especially C₁₋₄ alkyl, and each Q² is hydrogen.

Both homopolymer and copolymer PPE are included. The preferredhomopolymers are those containing 2,6-dimethyl-1,4-phenylene etherunits. Suitable copolymers include random copolymers containing, forexample, such units in combination with 2,3,6-trimethyl-1,4-phenyleneether units. Also included are PPE containing moieties prepared bygrafting vinyl monomers or polymers such as polystyrenes, as well ascoupled PPE in which coupling agents such as low molecular weightpolycarbonates, quinones, heterocycles and formals undergo reaction inknown manner with the hydroxy groups of two PPE chains to produce ahigher molecular weight polymer.

It will be apparent to those skilled in the art from the foregoing thatthe PPE contemplated for use in the present invention include all thosepresently known, irrespective of variations in structural units orancillary chemical features.

The PPE generally have an intrinsic viscosity (I.V.) often between about0.10-0.60 dl./g., preferably in the range of about 0.25-0.48 dl./g., allas measured in chloroform at 25° C. It is also possible to utilize ahigh intrinsic viscosity PPE and a low intrinsic viscosity PPE incombination. Determining an exact ratio, when two intrinsic viscositiesare used, will depend somewhat on the exact intrinsic viscosities of thePPE used and the ultimate physical properties that are desired. It ispreferred that the polyphenylene ether resin be present at about 5 toabout 70 percent by weight based on the weight of the entirecomposition.

The PPE resin compositions of the present invention optionally containat least one nonelastomeric polymer of an alkenylaromatic compound.Suitable polymers of this type may be prepared by methods known in theart including bulk, suspension and emulsion polymerization. Theygenerally contain at least about 25% by weight of structural unitsderived from an alkenylaromatic monomer of the formula (II):

wherein G is hydrogen, lower alkyl or halogen; Z is vinyl, halogen orlower alkyl; and p is from 0 to 5. These resins include homopolymers ofstyrene, chlorostyrene and vinyltoluene, random copolymers of styrenewith one or more monomers illustrated by acrylonitrile, butadiene,α-methylstyrene, ethylvinylbenzene, divinylbenzene and maleic anhydride,and rubber-modified polystyrenes comprising blends and grafts, whereinthe rubber is a polybutadiene or a rubbery copolymer of about 98-68%styrene and about 2-32% diene monomer. These rubber modifiedpolystyrenes include high impact polystyrene (commonly referred to asHIPS). Non-elastomeric block copolymer compositions of styrene andbutadiene can also be used that have linear block, radial block ortapered block copolymer architectures. They are commercially availablefrom such companies as Fina Oil as under the trademark FINACLEAR andPhillips under the trademark K-RESINS.

The amount of the polymer of a nonelastomeric alkenylaromatic compound,when one is used, is an amount effective to improve the flow andprocessability of the composition. Improved flow can be indicated byreduced viscosity or reduced injection pressures needed to fill a partduring an injection molding process. Generally, the nonelastomericalkenylaromatic compound is utilized in the range of about 20% to about60% by weight based on the total weight of the composition. Thepreferred range is about 30% to about 60% by weight; based on the totalweight of the composition.

The compositions of the present invention may also contain at least oneimpact modifier. The impact modifier may be used alone or in combinationwith a nonelastomeric alkenylaromatic compound. The impact modifiersinclude block (typically diblock, triblock or radial teleblock)copolymers of alkenyl aromatic compounds and dienes. Most often at leastone block is derived from styrene and at least one block from at leastone of butadiene and isoprene. Especially preferred are the triblock anddiblock copolymers comprising polystyrene blocks and diene derivedblocks wherein the aliphatic unsaturation has been preferentiallyremoved with hydrogenation. Mixtures of various copolymers are alsosometimes useful. The weight average molecular weights of the impactmodifiers are typically in the range of about 50,000 to 300,000. Blockcopolymers of this type are available commercially from a number ofsources, including Phillips Petroleum under the trademark SOLPRENE,Shell Chemical Co. under the trademark KRATON, and Kuraray under thetrademark SEPTON.

Various mixtures of the aforementioned impact modifiers are alsosometimes useful. The amount of the impact modifier generally present,when one is used, is an amount effective to improve the physicalproperties, for example, the ductility of the composition when comparedto the same composition without an impact modifier. Improved ductilitycan be indicated by increased impact strength, increased tensileelongation to break, or both increased impact strength and increasedtensile elongation to break Generally, when an impact modifier ispresent, it is utilized in the range of about 1% to about 20% by weightbased on the total weight of the composition. A preferred range is about1% to about 8% by weight; based on the total weight of the composition.The exact amount and types or combinations of impact modifiers utilizedwill depend in part on the requirements needed in the final blendcomposition.

Organic phosphate compounds are another component of the presentinvention. The organic phosphate is preferably an aromatic phosphatecompound of the formula (III):

where R is the same or different and is alkyl, cycloalkyl, aryl, alkylsubstituted aryl, halogen substituted aryl, aryl substituted alkyl,halogen, or a combination of any of the foregoing, provided at least oneR is aryl.

Examples include phenyl bisdodecyl phosphate, phenylbisneopentylphosphate, phenyl-bis(3,5,5′-tri-methyl-hexyl phosphate), ethyldiphenylphosphate, 2-ethyl-hexyldi(p-tolyl) phosphate, bis-(2-ethylhexyl)p-tolylphosphate, tritolyl phosphate, bis-(2-ethylhexyl) phenylphosphate, tri-(nonylphenyl) phosphate, di(dodecyl) p-tolyl phosphate,tricresyl phosphate, triphenyl phosphate, dibutylphenyl phosphate,2-chloroethyldiphenyl phosphate, p-tolyl bis(2,5,5′-trimethylhexyl)phosphate, 2-ethylhexyldiphenyl phosphate, and the like. The preferredphosphates are those in which each R is aryl. Especially preferred istriphenyl phosphate, which may be either unsubstituted or substituted,for example, isopropylated triphenyl phosphate.

Alternatively, the organic phosphate can be a di- or polyfunctionalcompound or polymer having the formula

or

or

including mixtures thereof, in which R¹, R³ and R⁵ are, independently,hydrocarbon; R², R⁴, R⁶ and R⁷ are, independently, hydrocarbonoxy; X¹,X² and X³ are halogen; m and r are 0 or integers from 1 to 4, and n andp are from 1 to 30.

Examples include the bis diphenyl phosphates of resorcinol, hydroquinoneand bisphenol-A, respectively, or their polymeric counterparts.

Methods for the preparation of the aforementioned di- and polyfunctionalaromatic phosphates are described in British Patent No. 2,043,083.

Another development is the use of certain cyclic phosphates, forexample, diphenyl pentaerythritol diphosphate, as a flame retardantagent for polyphenylene ether resins, as is described by Axelrod in U.S.Pat. No. 4,254,775.

Also suitable as flame-retardant additives for this invention arecompounds containing phosphorus-nitrogen bonds, such as phosphonitrilicchloride, phosphorus ester amides, phosphoric acid amides, phosphonicacid amides, phosphinic acid amides, tris(aziridinyl) phosphine oxide,or tetrakis(hydroxymethyl) phosphonium chloride. These flame-retardantadditives are commercially available.

Preferred phosphate flame retardants include those based upon resorcinolsuch as, for example, resorcinol tetraphenyl diphosphate, as well asthose based upon bis-phenols such as, for example, bis-phenol Atetraphenyl diphosphate. Phosphates containing substituted phenyl groupsare also preferred. In an especially preferred embodiment, theorganophosphate is selected from the group consisting of butylatedtriphenyl phosphate ester, resorcinol tetraphenyl diphosphate,bis-phenol A tetraphenyl diphosphate, and mixtures containing at leastone of the foregoing.

In the preparation of the concentrate of PPE with the organic phosphateit is desirable to have a relatively large amount of the organicphosphate present so as to result in a high value concentrate. By highvalue is meant that the concentrate can be let-down to a relativelylarge degree in order to prepare a wide variety of final formulationsfrom a single concentrate composition. It is preferred that theconcentrate contain at least 5%, preferably at least 15%, and mostpreferably at least about 20% or more organic phosphate compound byweight based upon the weight of the PPE. The maximum amount of phosphatecompound that can be present can also vary widely and is generallylimited by the maximum amount that can be added before the concentratesbecomes sticky and begins to agglomerate. This amount is generally lessthan about 50% by weight of organic phosphate based on the total weightof the PPE/organic phosphate concentrate.

In the final composition, the flame retardant is present in at least theminimum amount necessary to impart a degree of flame retardancy to thecomposition to pass the UL-94 protocol at a rating of V-0, V-1, or V-2depending on the specific application requirements. The particularamount will vary, depending on the molecular weight of the organicphosphate, the amount of the flammable resin present and possibly othernormally flammable ingredients which might also be included in thecomposition.

For compositions comprising polyphenylene ether resin, preferredcompositions have the major components which make up the composition inan amount within the following preferred ranges:

Polyphenylene ether resin, (a) about 30 to about 70 parts;

Non-elastomeric polymer of an alkenylaromatic compound, (b) about 20 toabout 60 parts; and

Organic phosphate, (c) about 10 to about 30 parts;

based on 100 parts by weight of (a), (b), and (c) together.

Compositions of the present invention can also include effective amountsof at least one additive selected from the group consisting ofthermoplastic resins such as, for example, polyolefins, polyetherimides,polyethersulfones, polysulfones, polyamides, polyesters, and polyarylenesulfides, compatibilizers, impact modifiers, anti-oxidants, dripretardants, crystallization nucleators, dyes, pigments, colorants,synergists, reinforcing agents, fillers, stabilizers, and antistaticagents. These additives are known in the art, as are their effectivelevels and methods of incorporation. Effective amounts of the additivesvary widely, but they are usually present in an amount up to about 60%or more by weight, based on the weight of the entire composition.

The resin compositions used in the present invention can be prepared bya variety of methods involving intimate admixing of the materials withany additional additives desired in the formulation. Suitable proceduresinclude solution blending and melt blending. Because of the availabilityof melt blending equipment in commercial polymer processing facilities,melt processing procedures are generally preferred. Examples ofequipment used in such melt compounding methods include: co-rotating andcounter-rotating extruders, single screw extruders, disc-pack processorsand various other types of extrusion equipment. In some instances, thecompounded material exits the extruder through small exit holes in a dieand the resulting strands of molten resin are cooled by passing thestrands through a water bath. The cooled strands can be chopped intosmall pellets for packaging and further handling.

All of the ingredients may be added initially to the processing system,or else certain additives may be pre-compounded with each other as inthe case of the concentrates of the present disclosure. It is sometimesadvantageous to introduce the organic phosphate compound as a liquidinto the compounder through the use, for example, of a liquid injectionsystem as is known in the compounding art. It is also sometimesadvantageous to employ at least one vent port in each section betweenthe feed ports to allow venting (either atmospheric or vacuum) of themelt. Those of ordinary skill in the art will be able to adjust blendingtimes and temperatures, as well as component addition location andsequence, without undue additional experimentation.

It should also be clear that improved molded articles prepared from thecompositions of the present invention represent an additional embodimentof this invention.

All patents cited by reference are incorporated by reference herein.

The following examples are provided to illustrate some embodiments ofthe present invention. They are not intended to limit the invention inany aspect. All percentages are by weight based on the total weight ofthe entire composition, unless otherwise indicated.

EXPERIMENTAL

The following examples are illustrative of the compositions of thepresent invention.

Compositions were evaluated comparing PPE in the form of (1) powder(control), (2) ground into a particle size of less than about 3 mm byabout 3 mm, (3) pellets having a size of about 1 mm by 3 mm (mini), and(4) pellets having a size of 3 mm by 3 mm (regular). To contrast thecompositions derived directly from PPE, concentrates of PPE with eitherHIPS or a phosphate flame retardant (e.g., tetraphenyl resorcinoldiphosphate: “RDP”) were also evaluated as either pellets having a sizeof 3 mm by 3 mm (regular), or alternatively as ground into a particlesize of less than about 3 mm by about 3 mm. The energy input into thePPE was varied as “high” by addition of the PPE into the first barrel ofan eleven barrel twin-screw extruder, or “low” by addition of the PPEinto the seventh barrel of an eleven barrel twin-screw extruder. TheI.V. of the PPE was varied between 0.33, 0.40, and 0.46. The standardfinal formulation was as follows with all parts by weight: PPE: 41.75;HIPS: 37.22; tetraphenyl resorcinol diphosphate: 17.6;polystyrene-poly(butadiene)-polystyrene block copolymer: 1.7; LLDPE:1.1; tridecylphosphite: 0.39; ZnO: 0.1; ZnS: 0.1: TSAN: 0.2.

The compositions were extruded on a Werner-Pfleiderer twin-screwextruder at a temperature of about 280-320° C. with vacuum applied tothe melt during compounding. For concentrates, the vacuum level istypically low, e.g., 0 to about 3 inches. For final compositions, thevacuum level is typically higher, e.g., about 3 to about 30 inches. Theresultant compositions were molded using a van Dorn injection moldingmachine using a temperature set of about 275-300° C. and a moldtemperature of about 80-110° C. Samples of the compositions were alsosubjected to measurement of notched Izod impact strength according toASTM D256 (employing a sample size of 2.5 inch by 0.5 inch by 0.125inch), Dynatup (energy to fracture, falling dart test) strengthaccording to ASTM D3763 (using 4 inch diameter by 0.125 inch disks),flexural modulus and flexural strength according to ASTM D790 (employinga sample size of 6 inch by 0.5 inch by 0.25 inch), and tensile yield andtensile elongation at break according to ASTM D638.

TABLE 1 Sample 1 2 3 4 5 6 Energy Input High Low High Low High Low PPEIV 0.33 0.33 0.4 0.4 0.46 0.46 Pellet Type¹ R R R R R R Properties HDT @264 psi ° F. 172.3 170.8 170.7 168.5 168 168.6 Notched Izod, 73° F.ft-lb/in 1.87 2.18 3.5 4.23 3.43 3.6 std. dev. 0.038 0.198 0.684 0.8470.292 0.153 Notched Izod, −20° F. ft-lb/in 1.36 1.5 1.62 1.62 1.61 1.45std. dev. 0.045 0.113 0.136 0.125 0.127 0.058 Energy to Failure, 73° F.ft-lb 8.93 10.27 11.62 9.47 7.99 12.42 std. dev. 2.5 3.65 4.56 3.19 2.742.61 Total Energy, 73° F. ft-lb 12.01 14.57 17.68 18.93 12.97 15.45 std.dev. 3.79 4.68 3.81 1.54 0.95 1.49 Energy to Failure, −20° F. ft-lb 1.921.58 2.66 2.71 3.74 3.16 std. dev. 0.45 0.48 0.87 1.87 1.85 2.39 TotalEnergy, −20° F. ft-lb 2.18 1.93 2.89 3.41 5 3.82 std. dev. 0.38 0.460.72 2.02 1.89 2.13 Flexural Modulus, 73° F. kpsi 346 347 343 343 344342 std. dev. kpsi 4.6 1.5 3.2 0.9 1.6 0.7 Flex Str. @ yield, 73° F. psi11020 10930 11110 11040 10970 10920 std. dev. 189 43 20 47 34 60 Flex E.@ break, 73° F. lb-in 34.66 35.04 35.39 34.91 34.48 34.87 std. dev. 0.460.8 0.99 0.84 0.38 0.66 Ten. Str. @ yield, 73° F. psi 7936 7757 78267877 7750 7765 std. dev. 20 34 63 63 31 15 Ten. Str. @ break, 73° F. psi6498 6591 6705 6824 6893 6969 std. dev. 169 50 85 106 90 60 T. Elong. @break, 73° F. % 28.47 25.92 25 23.64 20.21 17.18 std. dev. 1.93 1.252.21 3.86 1.24 1.44 Sample 7 8 9 10 11 12 Energy Input High Low High LowHigh Low PPE IV 0.33 0.33 0.4 0.4 0.46 0.46 Pellet Type¹ M M M M M MProperties HDT @ 264 psi ° F. 171.3 170.5 171.8 167.2 171.2 170 NotchedIzod, 73° F. ft-lb/in 1.89 2 3.22 4.48 4.04 3.37 std. dev. 0.112 0.0980.14 0.589 0.438 0.191 Notched Izod, −20° F. ft-lb/in 1.34 1.4 1.55 1.711.52 1.65 std. dev. 0.166 0.038 0.144 0.127 0.128 0.139 Energy toFailure, 73° F. ft-lb 8.41 11.6 14.07 11.03 10.31 9.38 std. dev. 4.582.47 2.82 1.36 3.8 4.17 Total Energy, 73° F. ft-lb 14.49 12.81 19.7719.11 15.99 13.7 std. dev. 2.04 3.44 2.79 2.1 0.88 1.22 Energy toFailure, −20° F. ft-lb 1.78 2.12 2.36 1.77 2.29 2.54 std. dev. 0.56 0.480.63 0.33 0.99 0.81 Total Energy, −20° F. ft-lb 2.02 2.27 2.55 2.14 2.754.88 std. dev. 0.56 0.49 0.58 0.41 0.72 1.91 Flexural Modulus, 73° F.kpsi 347 341 348 344 347 343 std. dev. kpsi 4.9 4.2 4.7 1.7 2.9 2.2 FlexStr. @ yield, 73° F. psi 10910 10880 11210 11200 11320 11080 std. dev.37 107 185 42 147 56 Flex E. @ break, 73° F. lb-in 34.76 34.95 35.1735.72 35.4 35.25 std. dev. 0.62 0.45 0.78 0.87 0.41 0.47 Ten. Str. @yield, 73° F. psi 7725 7666 7930 7906 7930 7885 std. dev. 42 103 20 1572 80 Ten. Str. @ break, 73° F. psi 6432 6343 6809 6674 7032 7175 std.dev. 134 286 134 193 101 92 T. Elong. @ break, 73° F. % 29.88 29.9223.86 25.62 19.03 14.85 std. dev. 2.29 4.54 2.49 2.23 2.29 1.46 ¹R =pellet of 3 mm by 3 mm; M = pellet of 1 mm by 3 mm; G = ground to lessthan 3 mm by 3 mm; P = powder - control

TABLE 2 Sample 13 14 15 16 17 18 19 20 21 Energy Input High Low High LowHigh Low High High High PPE IV 0.33 0.33 0.4 0.4 0.46 0.46 0.33 0.4 0.46Pellet Type¹ G G G G G G P P P Properties HDT @ 264 psi ° F. 167.9 169.3172 171.6 170.8 170 167.8 168.7 172.2 Notched Izod, ft-lb/in 1.95 2.224.29 4.77 4.91 5.02 2 3.81 5.77 73° F. std. dev. 0.118 0.067 0.812 0.1350.246 0.282 0.064 0.791 0.236 Notched Izod, ft-lb/in 1.27 1.45 1.63 1.691.72 1.63 1.45 1.72 1.85 −20° F. std. dev. 0.036 0.079 0.106 0.056 0.060.12 0.094 0.148 0.139 Energy to Failure, ft-lb 15.38 13.72 22.56 21.0319.71 25.3 20.74 36.1 31.3 73° F. std. dev. 4.21 3.47 1.95 6.76 6.381.86 8.73 2.62 7.8 Total Energy, ft-lb 17.61 17.17 26.14 25.83 24.5432.53 24.73 36.4 34.76 73° F. std. dev. 3.48 1.86 4.87 7.7 5.9 1.48 3.732.6 5.65 Energy to Failure, ft-lb 2.79 3.91 3.24 3 3.46 3.62 4.75 7.998.55 −20° F. std. dev. 0.96 1.38 0.84 1.12 0.94 0.82 1.02 3.68 4.94Total Energy, ft-lb 2.95 4.01 3.4 3.15 3.69 4.19 4.83 8.1 8.66 −20° F.std. dev. 0.87 1.31 0.72 1.03 0.78 0.35 0.95 3.59 4.89 Flexural Modulus,kpsi 338 343 346 345 348 349 336 332 336 73° F. std. dev. kpsi 1.6 1.61.3 0.5 1.5 2.1 2.7 1.2 3.1 Flex Str. @ yield, psi 10670 10950 1120011110 11290 11350 10780 10820 11150 73° F. std. dev. 8 12 31 34 27 89 399 29 Flex E. @ break, lb-in 33.58 34.77 35.37 34.89 35.71 35.85 34.0534.16 35.56 73° F. std. dev. 0.42 0.17 0.44 0.21 0.46 0.91 0.66 0.580.42 Ten. Str. @ yield, psi 7542 7766 7960 7905 7986 7975 7592 7748 788073° F. std. dev. 9 21 9 15 9 18 35 14 84 T. Str. @ break, psi 6108 63456257 6244 6724 6382 5957 6042 6170 73° F. std. dev. 125 235 27 76 280152 114 10 86 T. Elong. @ break, % 32.69 27.95 32.43 29.31 24.65 31.1532.69 31.94 37.7 73° F. std. dev. 1.97 4.15 2.61 1.24 3.07 3.98 2.571.17 9.09 ¹R = pellet of 3 mm by 3 mm; M = pellet of 1 mm by 3 mm; G =ground to less than 3 mm by 3 mm; P = powder - control

The compositions in Tables 1 and 2 compare the same composition whereinthe form of the PPE has been varied. Samples 19 to 21 illustratecontrols varying the I.V. of the PPE but using the PPE in the powderform as commercially isolated and available. The physical propertiesobtained with these compositions illustrate the target values that wouldbe desired if the PPE were utilized in an alternate form to that ofisolated powder in the same or a new process. Samples 1 to 6 illustratethe physical properties obtained for the same composition varying theI.V. of the PPE but wherein the PPE is in a pellet form having anaverage size of about 3 mm by about 3 mm. Comparing the properties ofsamples 1 and 2 to control sample 19 of the same I.V. PPE; or samples 3and 4 to control sample 20; or samples 5 and 6 to control sample 21demonstrates the substantially poorer impact strength, especiallyDynatup dart impact strength obtained when pellets having an averagesize of about 3 mm by about 3 mm are utilized. Likewise, the propertiesof samples 7 and 8 to control sample 19 of the same I.V. PPE; or samples9 and 10 to control sample 20; or samples 11 and 12 to control sample 21demonstrates the substantially poorer impact strength, especiallyDynatup dart impact strength obtained when mini-pellets having anaverage size of about 3 mm by about 3 mm are utilized.

In contrast to the results using pellets or mini-pellets, the propertiesof samples 13 and 14 to control sample 19 of the same I.V. PPE; orsamples 15 and 16 to control sample 20; or samples 17 and 18 to controlsample 21 demonstrates the substantially better physical propertiescould be obtained using ground material. It was unexpected that thephysical properties, especially the Dynatup dart impact strength,(labeled “Total Energy, 73° F.” in the Tables), would be affected by thePPE particle size. It is thought that using a smaller PPE particle thanthe standard 3 mm by 3 mm pellet, and/or the irregular shape of theground particles, affords less shear heating during the compoundingoperation with less thermal and shear degradation of the materials.

TABLE 3 Sample 22 23 24 25 26 27 28 29 PPE/HIPS ratio 90:10 90:10 — —70:30 70:30 — — PPE/RDP ratio — — 90:10 90:10 — — 70:30 70:30 EnergyInput High High High High High High High High PPE IV 0.40 0.46 0.40 0.460.40 0.46 0.40 0.46 Pellet Type¹ G G G G G G R R Properties HDT @ 264psi ° F. 173 177 172.6 201.7 177.7 179.1 174.2 173.2 Notched Izod, 73°F. ft-lb/in 3.0 3.1 4.31 5.29 3.83 4.01 5.74 6.61 std. dev. 0.195 0.310.86 0.22 0.302 0.292 0.373 0.2 Notched Izod, −20° F. ft-lb/in 1.9 1.92.48 3.0 1.93 2.16 2.53 2.9 std. dev. 0.384 0.384 0.23 0.189 0.235 0.4140.278 0.417 Energy to Failure, 73° F. ft-lb 6.97 12.32 8.44 9.84 11.5212.72 21.58 26.85 std. dev. 1.87 1.82 3.36 6.4 4.84 6.67 4.84 5.06 TotalEnergy, 73° F. ft-lb 15.94 13.0 15.52 19.53 18.14 19.41 26.88 29.86 std.dev. 0.74 1.6 0.77 4.36 2.39 3.37 5.23 3.33 Energy to Failure, −20° F.ft-lb 1.59 2.87 2.75 4.69 2.51 4.7 3.88 3.07 std. dev. 0.26 0.69 1.344.62 0.72 4.06 1.3 0.36 Total Energy, −20° F. ft-lb 1.63 3.14 4.98 7.342.68 5.81 3.93 5.32 std. dev. 0.26 0.46 2.59 3.44 0.83 4.02 1.3 2.25Flexural Modulus, 73° F. kpsi 347 344 363.7 368.7 344.3 348.9 343.3344.7 std. dev. kpsi 2.574 4.7 3.8 3.6 2307 180 2 1.6 Flex Str. @ yield,73° F. psi 11500 11350 11290 12340 11320 11610 11400 11450 std. dev. 28104 260 130 63 28 84 30 Flex E. @ break, 73° F. lb-in — — 37.75 40.05 —— 37.64 37.77 std. dev. 0.6 0.15 — — 0.35 0.25 Ten. Str. @ yield, 73° F.psi 7720 7681 7512 8023 7533 7671 7763 7682 std. dev. 16 10 90 54 23 1513 51 T. Str. @ break, 73° F. psi 6429 6735 6287 6843 6005 6231 60855977 std. dev. 156 58 106 491 43 222 96 71 T. Elong. @ break, 73° F. %22.67 19.16 30.36 25.53 30.32 29.79 25.59 25.54 std. dev. 1 1.33 2.033.59 1.27 2.65 2.5 1.41 ¹R = pellet of 3 mm by 3 mm; M = pellet of 1 mmby 3 mm; G = ground to less than 3 mm by 3 mm; P = powder - control

The data in Table 3 compares concentrate compositions containing PPEwith either HIPS or RDP. As can be seen from these data, especiallycomparing samples 26 and 27 to 28 and 29 with a 30% by weight loading ofthe HIPS or RDP, respectively, high value concentrates can be made fromPPE with phosphate materials. It was unexpected that concentratescontaining so high a loading of phosphate would result in suchacceptable physical properties. It was especially unexpected that thedart impact strength values would be so high. The results are alsounexpected considering that the PPE/ phosphate concentrates of samples28 and 29 were used as pellets and not as ground material.

It should also be clear that the present invention affords a method toprepare PPE compositions while reducing the dust explosion tendency ofPPE powder.

The preceding examples are set forth to illustrate specific embodimentsof the invention and are not intended to limit its scope. It should beclear that the present invention includes articles from the compositionsas described herein. Additional embodiments and advantages within thescope of the claimed invention will be apparent to one or ordinary skillin the art.

We claim:
 1. A process for the manufacture of a thermoplasticcomposition comprising at least one polyphenylene ether resin and atleast one polystyrene resin wherein the process comprises: preparing asolid concentrate comprising a polyphenylene ether resin and at leastabout 5% by weight of an organic phosphate compound based on the weightof the polyphenylene ether resin in the concentrate, wherein the solidconcentrate has less than 5% by weight of particles less than about 75microns in size; and blending the solid concentrate with the polystyreneresin.
 2. The process of claim 1, wherein the solid concentrate hasessentially no particles less than about 75 microns in size.
 3. Theprocess of claim 1, wherein the solid concentrate contains at leastabout 15% by weight of the organic phosphate compound based upon theweight of the polyphenylene ether resin in the concentrate.
 4. Theprocess of claim 1, wherein the solid concentrate contains at leastabout 20% by weight of the organic phosphate compound based upon theweight of the polyphenylene ether resin in the concentrate.
 5. Theprocess of claim 1, wherein the polyphenylene ether resin is presentfrom about 5 to about 70 percent by weight based upon the weight of theentire thermoplastic composition.
 6. The process of claim 1, wherein theorganic phosphate compound comprises at least one of the groupconsisting of:

and mixtures thereof, in which R¹, R³ and R⁵ are, independently,hydrocarbon; R², R⁴, R⁶ and R⁷ are, independently, hydrocarbonoxy; X¹,X² and X³ are halogen; m and r are 0 or integers from 1 to 4 , and n andp from 1 to
 30. 7. The process of claim 1, wherein the organic phosphatecompound comprises at least one of the group consisting of: phenylbisdodecyl phosphate, phenylbisneopentyl phosphate, phenyl-bis(3,5,5′-tri- methyl-hexyl phosphate), ethyldiphenyl phosphate,2-ethyl-hexyldi(p-tolyl) phosphate, bis-(2-ethylhexyl) p-tolyphosphate,tritolyl phosphate, bis-(2-ethylhexyl) phenyl phosphate,tri-(nonylphenyl) phosphate, di (dodecyl) p-tolyl phosphate, tricresylphosphate, triphenyl phosphate, dibutylphenyl phosphate,2-chloroethyldiphenyl phosphate, p-tolyl bis(2,5,5′-trimethylhexyl)phosphate, and 2-ethylhexyldiphenyl phosphate.
 8. The process of claim1, further comprising blending the solid concentrate with an additiveselected from the group consisting of stabilizers, dyes, dripsuppressers, pigments, and mixtures thereof.
 9. The process of claim 1,wherein the organic phosphate compound comprises bisphenol-A tetraphenyldiphosphate.
 10. The process of claim 1, wherein the organic phosphatecompound comprises resorcinol tetraphenyl diphosphate.
 11. The processof claim 1, wherein the organic phosphate compound is selected from thegroup consisting of butylated triphenyl phosphate ester, resorcinoltetraphenyl diphosphate, bis-phenol A tetraphenyl diphosphate, andmixtures thereof.
 12. A thermoplastic composition made by the process ofclaim
 1. 13. Articles formed out of the composition made by the processof claim
 1. 14. The process of claim 1, wherein the polyphenylene ethercomprises a plurality of structural units having the formula

wherein for each structural unit, each Q¹ is independently halogen,primary or secondary C₁-C₇ alkyl, phenyl, haloalkyl, aminoalkyl,hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atomsseparate the halogen and oxygen atoms; and each Q² is independentlyhydrogen, halogen, primary or secondary C₁-C₇ alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹.
 15. The processof claim 1, wherein the polyphenylene ether comprises2,6-dimethyl-1,4-phenylene ether units.
 16. The process of claim 1,wherein the polyphenylene ether comprises 2,6-dimethyl-1,4-phenyleneether units and 2,3,6-trimethyl-1,4-phenylene ether units.
 17. A processfor the manufacture of a thermoplastic composition comprising at leastone polyphenylene ether resin wherein the process comprises preparing asolid concentrate comprising a polyphenylene ether resin and at leastabout 5% by weight of an organic phosphate compound based on the weightof the polyphenylene ether resin in the concentrate, wherein the solidconcentrate has less than 5% by weight of particles less than about 75microns in size.
 18. The process of claim 17, further comprisingblending the solid concentrate with at least one additive selected fromthe group consisting of polyolefins, polyetherimides, polyethersulfones,polysulfones, polyamides, polyesters, polyarylene sulfides,compatibilizers, impact modifiers, anti-oxidants, drip retardants,crystallization nucleators, dyes, pigments, colorants, synergists,reinforcing agents, fillers, stabilizers, and antistatic agents.